1. Field of the Invention
This invention relates to rider roll assemblies, and particularly to rider roll assemblies for paper winding devices.
2. Prior Art
Paper winding devices which wind paper on a paper roll core frequently utilize parallel rotating winder drums with the paper passed between a nip formed between the roll core and the winder drums. Rotation of the winder drums causes rotation of the paper roll core and the spiral wrapping of the paper around the core. As the roll of paper builds, the core position with respect to the winder drums changes to reflect the increasing diameter of the paper roll. In order to control nip pressure, initially between the paper roll core and winder drums and later between the paper roll itself and winder drums, a rider roll may be urged against the paper roll core, initially, and later the paper roll, in a direction to affect the nip pressure.
The rider roll must be capable of movement away from the winder drums to allow for increase in paper roll diameter. Moreover, since the nip pressure is increased as the diameter of the paper roll increases as a result of the increased weight of the paper roll, means are normally provided for controlled reduction of the rider roll force as the paper roll weight increases. Further, in order to allow removal of the roll of paper from the winder drums, it is necessary to remove the rider roll from any position of interference. To this end rider rolls are frequently carried by a rider roll beam assembly having sufficient mass to provide the maximum initial nip force. The rider roll beam is normally movable in a beam guide in directions towards and away from the paper roll core. To provide fur such movement, chains are affixed to the rider roll beam adjacent axial ends of the beam. The chains are entrained over a common cross shaft having chain engaging sprockets non-rotatably affixed thereto. The chains, after passing over the sprockets, are then connected to a rider roll force and position control system which may, for example, include pneumatic cylinders and counter weights.
By use of a common cross shaft having sprockets engaged by the chains from each end of the rider roll beam, with the sprockets non-rotatably affixed to the cross shaft, the cross shaft can function as a torsional rider roll level maintenance device.
Frequently, as the paper roll begins for form, due to minute paper thickness differences along the transverse width of the paper and/or other reasons including rider roll nip force, one side of the paper roll may increase in diameter at a rate greater than the other side. When this occurs the rider roll will tend to become unlevel or non-parallel to the axis of the paper roll. In such a situation the cross shaft will act as a torsion bar to reduce the nip pressure at the low end of the rider roll and increase it at the high end and will thereby seek to maintain the rider roll level. This can, however, in some instances, result in damage to the paper by providing an undesired nip pressure at either the high or the low end. Too high a nip pressure at the high end of the rider roll can result in paper stretching while too low a nip pressure at the low end can result in a loose wrap which can allow paper shifting to occur between successive windings.
In spite of the possible occurrence of such deficiencies in the use of torsion cross shafts, such shafts are desired in the maintenance of desired levelism of the rider roll as well as for the provision of some increase in nip force at the high end of the paper roll.
It would therefore be an advance in the art to provide a rider roll assembly which utilizes a torsion shaft for maintenance of rider roll levelism, but in which the nip force disparity between high and low ends of the rider roll is responsive to the degree of diameter difference between the high and low ends of the paper roll and which can be controlled.
It would be a further advantageous advance to provide a rider roll system where the initial levelism of the rider roll could be adjusted and where nip pressures at the respective ends of the rider rolls could be varied.